Generally, mass spectrometers measure ions created from samples, enabling identification and quantitation of the molecular contents of the samples. Mass spectrometers include an ion source for ionizing the samples for subsequent focusing, filtering, detection and analysis. The ion source includes, for example, an ion volume (i.e., a small section of the ion source in which ionization occurs), one or more ionizing elements (e.g., a structure that typically contains a filament wire, such as tungsten or rhenium, an electron reflector, contact pins and a support piece), and one or more ion focusing elements, such as electrostatic lenses. The interior surfaces of the ion volume and lenses become contaminated with use. Furthermore, the filament wire of the ionizing elements will break after many hours of use making the entire filament structure, i.e., the ionizing elements, the most common consumable in a mass spectrometer. Because sensitivity and performance of the mass spectrometer depend on cleanliness of the ion source, which includes the ion volume and any focusing elements, and a functional ionizing mechanism, i.e., an intact filament wire with solid electrical connections, the ion source must be cleaned (completely or in part) and the ionizing elements replaced in accordance with routine maintenance practices.
Conventionally, the replacement process is very time consuming, typically requiring a minimum of about four hours. The mass spectrometer must be shut down and slowly cooled and vented, which necessarily includes losing the operating vacuum. In addition, performance of the replacement ion source is improved if it is allowed to bake and equilibrate for eight or more hours (e.g., overnight). Most of the time required for the conventional ion source replacement process is incurred to accommodate cooling and venting the mass spectrometer, followed by heating and achieving acceptable levels of vacuum and background once the replacement ion source has been installed. The time required to actually exchange the contaminated ion source with a clean ion source, or replace a filament assembly (e.g., an ionizing element) is relatively short; that is, once the mass spectrometer has been cooled and vented to atmospheric pressure.
Conventionally, an ion volume can be removed from a mass spectrometer without shutting down and breaking vacuum (U.S. Patent Application Publication No. 2009/0242747). However, removing the ionizing elements, e.g., filament assembly, typically requires shutting down, due to the complexity of the structure and necessity for robust electrical connections.